What is the recommended dosage of atomoxetine (Strattera) in children?

Atomoxetine Dosage in Children

Initial Dosing

For children and adolescents weighing ≤70 kg, initiate atomoxetine at 0.5 mg/kg/day and increase after a minimum of 3 days to a target dose of 1.2 mg/kg/day, with a maximum of 1.4 mg/kg/day or 100 mg daily (whichever is less). 1

Weight-Based Dosing Protocol

• Children ≤70 kg:

  • Start: 0.5 mg/kg/day 1
  • Wait minimum 3 days before increasing 1
  • Target: 1.2 mg/kg/day 1
  • Maximum: 1.4 mg/kg/day or 100 mg daily, whichever is less 1

• Children and adolescents >70 kg:

  • Start: 40 mg/day 1
  • Wait minimum 3 days before increasing 1
  • Target: 80 mg/day 1
  • After 2-4 additional weeks, may increase to maximum 100 mg/day if response inadequate 1

Administration Schedule

• Atomoxetine can be given as a single morning dose OR divided into two doses (morning and late afternoon/early evening) 1
• May be taken with or without food 1
• Capsules must be swallowed whole, not opened 1

Titration Strategy

Increase doses gradually at 1-2 week intervals using the smallest available increments to minimize behavioral activation and optimize tolerability. 2

• Maintain initial dose for at least 1-2 weeks before increasing 2
• Increase by small increments (typically 10-25 mg) no more frequently than every 1-2 weeks 2
• If side effects occur, return to the previous well-tolerated dose 2

Critical Pitfall: Rapid Dose Escalation

• Behavioral activation/agitation (restlessness, insomnia, impulsiveness, aggression) can occur with rapid dose increases 2
• Younger patients are particularly susceptible to these effects 2
• Slow titration prevents unintentionally exceeding the optimal dose 2

Time to Therapeutic Effect

Set realistic expectations: atomoxetine requires 6-12 weeks to achieve full therapeutic effect, unlike stimulants which work within hours. 3, 2

• Maintain target dose for 4-6 weeks before judging efficacy 3
• No additional benefit demonstrated for doses >1.2 mg/kg/day in children 1

Special Populations Requiring Dose Adjustment

CYP2D6 Poor Metabolizers or Concurrent Strong CYP2D6 Inhibitors

For children taking strong CYP2D6 inhibitors (paroxetine, fluoxetine, quinidine) or known CYP2D6 poor metabolizers:

• Children ≤70 kg:

  • Start: 0.5 mg/kg/day 1
  • Increase to usual target of 1.2 mg/kg/day ONLY if symptoms fail to improve after 4 weeks AND initial dose is well tolerated 1

• Children >70 kg:

  • Start: 40 mg/day 1
  • Increase to 80 mg/day ONLY if symptoms fail to improve after 4 weeks AND initial dose is well tolerated 1

• Poor metabolizers (7% of population) have 10-fold higher plasma concentrations 4

Hepatic Impairment

• Moderate hepatic insufficiency (Child-Pugh Class B): Reduce initial and target doses to 50% of normal 1
• Severe hepatic insufficiency (Child-Pugh Class C): Reduce initial and target doses to 25% of normal 1

Evidence Supporting Efficacy

The 1.2 mg/kg/day target dose is supported by high-quality pediatric trials:

• In a dose-response study of 297 children ages 8-18, both 1.2 mg/kg/day and 1.8 mg/kg/day were superior to placebo and not different from each other, with 0.5 mg/kg/day showing intermediate efficacy 5
• The 1.2 mg/kg/day dose reduced ADHD symptoms by 34-38% versus 13-15.7% with placebo 6
• In autism spectrum disorder with comorbid ADHD, 1.2 mg/kg/day showed significant improvement in ADHD symptoms 7

Safety Monitoring

• Monitor for suicidality, clinical worsening, and unusual behavior changes, especially during initial months or dose changes 2
• Common adverse effects: nausea, vomiting, fatigue, decreased appetite, abdominal pain, somnolence 7, 2
• Screen for personal or family history of bipolar disorder before initiating treatment 1
• Discontinuation does not require tapering 1